IDT DNA Calculator
Estimate key oligo properties from sequence and OD260 data: length, GC%, molecular weight, extinction coefficient, concentration, total nmol, and reconstitution volume.
What is an IDT DNA calculator?
An IDT DNA calculator helps researchers quickly estimate oligonucleotide properties before or after ordering DNA. If you regularly work with primers, probes, or custom oligos, the most common questions are usually the same: “How many nanomoles do I have?”, “What concentration is this stock?”, and “How much volume do I need for a working solution?”.
This page gives you a practical, lab-friendly calculator for those day-to-day conversions. It uses commonly taught formulas for DNA concentration and composition so you can move fast at the bench. It is ideal when you need a quick answer without opening a full bioinformatics suite.
What this calculator estimates
- Sequence length (nt)
- Base composition (A, C, G, T counts)
- GC content (%)
- Approximate molecular weight (g/mol)
- Extinction coefficient (M-1cm-1)
- Concentration from OD260 (µM)
- Total amount (nmol) in the entered volume
- Approximate mass (µg)
- Reconstitution volume for a target concentration (optional)
- Rough melting temperature (Tm) for quick planning
How to use the tool
1) Paste your DNA sequence
Enter only the standard DNA bases: A, C, G, and T. You may include spaces or line breaks; they are ignored automatically. If any non-DNA letters are detected, the calculator will ask you to correct the input.
2) Enter OD260 and volume
OD260 is often measured by NanoDrop or cuvette-based UV spectrophotometry. Add the measured absorbance and the sample volume in µL. The calculator then estimates molar concentration and total quantity.
3) Add target concentration (optional)
If you know the stock concentration you want (for example 100 µM), provide it in the final field. The calculator returns the estimated reconstitution volume needed to reach that target.
4) Click calculate
Your results appear instantly in a structured table so you can copy values directly into your notebook or LIMS.
Formula notes (quick reference)
Molecular weight estimate
This calculator uses a common base-composition approximation for single-stranded DNA: MW = (A×313.21) + (C×289.18) + (G×329.21) + (T×304.20) + 79.0
Extinction coefficient estimate
Base-composition approximation: ε260 = (A×15400) + (C×7400) + (G×11500) + (T×8700)
Concentration and nmol from OD260
Assuming 1 cm path length, concentration in mol/L is estimated as OD260 / ε260. From there:
- µM = M × 1,000,000
- nmol = M × volume(µL) × 1000
Tm estimate
The tool reports a quick approximate Tm:
- For sequences shorter than 14 nt: 2(A+T) + 4(G+C)
- For sequences 14 nt or longer: 64.9 + 41×(GC−16.4)/N
Practical lab tips
- Use this as a planning tool; confirm critical values with your provider’s official analyzer when needed.
- For high-precision applications (qPCR probes, NGS adapters), nearest-neighbor thermodynamics are preferred over simple approximations.
- Double-check units every time (µL, mL, µM, nmol) to avoid 10x or 100x mistakes.
- If purity is low, OD260-based concentration may overestimate usable oligo.
- When sharing protocols, record both amount (nmol) and concentration (µM) for reproducibility.
Related searches and use cases
Many readers looking for an IDT DNA calculator also search for terms like oligo concentration calculator, OD260 to nmol converter, DNA molecular weight calculator, primer GC content calculator, and oligo reconstitution volume tool. This page is designed to cover those same everyday needs in one place.
Important disclaimer
This calculator provides educational and operational estimates. For regulated workflows, publication-grade thermodynamics, modified bases, or specialty chemistries, validate results with manufacturer documentation and your institutional SOPs.